Black liquor is a by-product of the papermaking process and is an aqueous solution of lignin residues, hemicellulose, and inorganic chemicals. Typically, the black liquor includes 40-45% soaps, 35-45% lignin, and 10-15% other organics. Lignin is a cross-linked racemic macromolecule with molecular masses in excess of ten thousand unified atomic mass units (10,000 u) and is relatively hydrophobic and aromatic. It is a natural polymer found in plant cell walls and wood, is readily available, relatively inexpensive, and is only less than that of cellulose in overall natural abundance.
Enormous amounts of lignin are produced as byproducts in the pulp and paper industry. In order for lignin to gain wider utilization as an inexpensive and biodegradable/biorenewable material, blends of lignin with thermoplastics are needed with enhanced mechanical and other useful properties. These enhanced properties should exceed those properties predictable by simple rules of mixing of the corresponding blends.